Either congenitally or by acquisition, abnormal openings or holes can occur between adjacent chambers of the heart or its associated major blood vessels. Such openings are referred to, respectively, as interatrial and interventricular septal defects or patent ductus arteriosus and aortico-pulmonary windows. Such openings cause blood to leak from one chamber or artery to another and result in decreased pumping efficiency of the heart. Similarly, if defects occur in the Foramen Ovale, such defects, referred to as Patent Foramen Ovale (PFO), may result in a cerebral embolism. These deformities usually are congenital, however, they can also occur following a heart attack, significantly complicating subsequent coronary treatment and recovery. Such defects typically impose added strain on the heart and ultimately may lead to heart failure if not corrected.
Traditionally, such defects have required extensive open chest surgical techniques for correction. Specifically, the repair of such defects required an open heart procedure in which the heart was exposed and then opened and the defect was sewn shut by direct suturing. In connection therewith, a patch of a synthetic prosthetic material such as Dacron, Teflon, silk, nylon or pericardium was used as a patch.
Although other methods of occluding defects, most notably the use of a plastic plug to occlude the defect, were suggested as early as the 1950s, such methods similarly require the use of open heart surgery to access the defect and place the prosthetic implant.
Beginning in the early 1970s, a number of devices and methods were proposed for the percutaneous transluminal catheterization procedure for the repair of intracardiac defects. For example, U.S. Pat. No. 3,874,388 to King, et al., describes a device in which a pair of umbrella-like occluders are positioned on opposite sides of a defect and drawn and locked together at a central hub which crosses the defect. The device is said to effectively occlude the defect. Although the King device and method proposed to eliminate the need to perform open heart surgery, its use and structure were very complicated in that generally they required the umbrella-like occluders to be opened manually once positioned at the defect.
Similarly, U.S. Pat. No. 4,007,743 to Blake relates to an umbrella-like defect closure device having a plurality of elongated struts pivotally mounted to a central hub. Each pair of adjacent struts is interconnected by a strip formed of a foldable, resilient material which serves to automatically and resiliently open each umbrella-like element once such element is released from a protective sheath. As in the King patent, the device includes two separate occluders which are locked together by a snap connection once each of the occluder segments has been individually positioned across the septal defect.
Still another defect closure device is described in U.S. Pat. No. 4,917,089 to Sideris. The Sideris patent relates to an apparatus and method for transvenous closure of a septal perforation in the heart. The closure apparatus comprises an occluder which is positioned on the distal side of the perforation and an occluder-holder which is positioned on the proximal side of the perforation and is connected to the occluder across the perforation by means of a so-called "button" closure. As in the earlier transluminally delivered occluders, the Sideris patent requires that device elements positioned on opposite sides of a septal defect are separately delivered to the site of the defect and connected to one another in situ.
Among the problems encountered with occluder devices of the designs described by King and Blake, is that they tend to be relatively rigid. In other words, the designs allow very little relative motion between the individual occluder elements and thereby require that each of said elements be placed precisely prior to seating at the septal wall and interconnection. In addition, because the devices described in the King and Blake patents include such relatively rigid structures, the devices are not particularly well suited for applications in which there is a variation in wall thickness at the site of the defect or in which the defect does not run perpendicularly through the septal wall.
Although the Sideris patent describes a device in which the occluder and occluder-holder are not rigidly interconnected, the Sideris device still requires that the occluder be placed precisely on the distal wall portion of the septum because defect occlusion is provided by a single occluder element. Thus, even though there is some amount of relative movement allowed between the occluder and the occluder-holder of the Sideris device, the arms of the occluder are rigid and the occluder section must be precisely positioned to cover the entire distal side of the defect in order to prevent blood from leaking through the defect and to prevent the device from becoming dislodged. Furthermore, like the King and Blake devices, the Sideris device requires in situ assembly to make interconnection between the occluder and the occluder-holder. Such an in situ assembly requirement complicates the occlusion procedure because it requires that the occluder be positioned precisely and then maintained in that position during the assembly step.
Accordingly, there is a need for a defect occlusion device and technique which eliminates the need to assemble or interconnect separate portions of the occluder in situ and which also allows some degree of relative movement or rotation between the individual occluder elements. There is also a need for a defect occlusion device which would allow the individual occluders of the device to be readily distinguished during a fluoroscopic visualization procedure.